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Risk Management Activities - Net Risk Management Assets and Liabilities (Details) - CAD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | $ 692
Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 4
Current | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | $ 90 | 85
Current | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (13) | 0
Long-term | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 452 | 607
Long-term | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 1 | 4
Financial Assets |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 530 | 696
Financial Assets | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 542 |
Financial Assets | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (12) |
Designated as a hedge | Cash flow hedges | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 676
Designated as a hedge | Cash flow hedges | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 0
Designated as a hedge | Current | Cash flow hedges | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 101 | 70
Designated as a hedge | Current | Cash flow hedges | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (9) | 0
Designated as a hedge | Long-term | Cash flow hedges | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 471 | 606
Designated as a hedge | Long-term | Cash flow hedges | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 0 | 0
Designated as a hedge | Financial Assets | Cash flow hedges |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 563 | 676
Designated as a hedge | Financial Assets | Cash flow hedges | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 572 |
Designated as a hedge | Financial Assets | Cash flow hedges | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (9) |
Not designated as a hedge | Financial Liabilities |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (33) |
Not designated as a hedge | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 16
Not designated as a hedge | Commodity risk management | Long-term |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (19) | 1
Not designated as a hedge | Commodity risk management | Current |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (11) |
Not designated as a hedge | Commodity risk management | Financial Liabilities |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (30) |
Not designated as a hedge | Other | Long-term |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 4
Not designated as a hedge | Other | Current |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 0
Not designated as a hedge | Other | Financial Liabilities |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 4
Not designated as a hedge | Current | Commodity risk management |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | 15
Not designated as a hedge | Current | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | (4) |
Not designated as a hedge | Long-term | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | 1 |
Not designated as a hedge | Financial Assets |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic |  | $ 20
Not designated as a hedge | Financial Assets | Other |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Risk exposure associated with instruments sharing characteristic | $ (3) |

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph B8 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_B8_c&doctype=Appendix&subtype=B -URIDate 2019-03-27 + Details
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